Potential Tropical Cyclone Two Forecast Discussion Number 4

By | July 11, 2019

Issued at 400 AM CDT Thu Jul 11 2019

000
WTNT42 KNHC 110846
TCDAT2
Potential Tropical Cyclone Two Discussion Number   4
NWS National Hurricane Center Miami FL       AL022019
400 AM CDT Thu Jul 11 2019
The convective activity associated with the broad area of low
pressure is still spread out, and the center of circulation
is not well defined at this time.  Both surface and scatterometer
data indicate that the winds remain near 25 kt.  The modest
northerly shear affecting the system should not hamper further
development.  Overall, the environmental conditions still favor the
formation of a tropical depression or a tropical storm later today,
and as the system moves over warm waters, strengthening is
indicated.  The intensity models are not as aggressive as they were
in previous runs, but still bring the disturbance to hurricane
status in about 48 hour or so, as the disturbance approaches the
coast.
During the past several hours, the low pressure area has barely
moved due to weak steering currents.  However, a westward or
260 degrees drift at about 4 kt should begin soon.  The system is
heading toward a weakness in the ridge, and this pattern should
induce a slow turn toward the west-northwest and then north
during the next 3 to 5 days.  The NHC track forecast continues to
be located on the western edge of the guidance envelope, and it has
been adjusted slightly eastward to be more consistent with the
multi-model ensemble TVCA.   It should be noted that track errors
are typically larger for potential tropical cyclones than more
mature systems.  In addition, the run-to-run consistency in the
track models has been poor, so confidence in the details of the
forecast is not high at the moment.
Key Messages:
1. A tropical depression is expected to form later today over the
northern Gulf of Mexico. Conditions appear favorable for this system
to strengthen to a hurricane that will bring storm surge, rainfall,
and wind hazards to the central Gulf Coast.
2. A dangerous storm surge is possible in portions of southern and
southeastern Louisiana where a Storm Surge Watch is in effect.
Additional storm surge watches may be needed later today. Residents
in these areas should monitor the progress of this system and listen
to any advice given by local officials.
3. A Hurricane Watch is in effect for much of the Louisiana coast
and additional tropical storm or hurricane watches and warnings
could be required. Residents in the watch area should ensure they
have their hurricane plan in place.
4. The slow movement of this system will result in a long duration
heavy rainfall threat along the central Gulf Coast and inland
through the lower Mississippi Valley through the weekend and
potentially into early next week. Flash flooding and river flooding
will become increasingly likely, some of which may be significant,
especially along and east of the track of the system.
FORECAST POSITIONS AND MAX WINDS
INIT  11/0900Z 27.5N  88.2W   25 KT  30 MPH...POTENTIAL TROP CYCLONE
12H  11/1800Z 27.5N  88.7W   30 KT  35 MPH
24H  12/0600Z 27.7N  89.5W   40 KT  45 MPH
36H  12/1800Z 28.0N  90.3W   50 KT  60 MPH
48H  13/0600Z 28.5N  91.1W   65 KT  75 MPH
72H  14/0600Z 31.0N  91.7W   45 KT  50 MPH...INLAND
96H  15/0600Z 33.5N  92.0W   30 KT  35 MPH...INLAND
120H  16/0600Z 36.0N  90.9W   20 KT  25 MPH...POST-TROP/REMNT LOW
$$
Forecaster Avila

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